It could not be tighter at the top and it was honours even - five points each from their back-to-back contests - after Perpignan ground out a 13-6 win against Worcester Warriors at Stade Aimé Giral that leaves the clubs locked together on 15 points in the chase for group honours and quarter-final qualification.
Both clubs will have rematches with Bizkiaia Gernika RT and Femi-CZ VEA Rovigo in the New Year and it could all come down to who performs best - and picks up bonus points - in those games as to who goes through to the prestigious last eight as the Pool winners.
It's advantage Perpignan who would take the spot if both clubs finish on the same points at the end of the Pool campaign as they lead Worcester based on the try count from their head to head matches 2 to 1.
Andy Goode, who contributed all the Warriors' points in their 22-21 win at Sixways in Round 3, scored the Premiership club's only points of a tense and tight first half with a 35th minute penalty goal.
The only try of the opening 40 minutes half came after just eight minutes with wing Richard Haughton cracking the Worcester defence, but the boot of Wales star James Hook did the rest of the damage in the first half with the conversion and penalty goals in the 33rd and 37th minutes.
It stayed on a knife edge into the second 40 minutes, Goode on target with another penalty as both clubs made a raft of replacements in an effort to introduce new energy into their efforts for this crucial contest.
But not even fresh legs could make a difference and this one is going all the way down to the wire.
